Production of building board

ABSTRACT

The invention relates to the reinforcement of the edges of cementitious board and especially plasterboard. Reinforcing strips are secured to at least one edge of the lower sheet employed in the manufacture of plasterboard and is incorporated with the sheet in the formed board as an edge reinforcement. The reinforcing strip may have any desired cross-section or profile but preferably has a channel section whereby the corners of the board are protected. It may also be grooved longitudinally to provide a kerfed edge to the board which is useful when securing the boards by means of concealed supports.

O United States Patent 11 1 1111 3,887,406 Gwynne June 3, 1975 [5 1 PRODUCTION OF BUILDING BOARD 3.367,8l8 2/1968 Voelker 16l/44 x 3.397,496 8/1968 Sohns 52/309 X [75] Inventor: Gwynne Loughbomugh' 3,546,841 12 1970 Smith et al.... l6I/44 x land 3,738,895 6/l973 Daymal r 264/47 X gnee Industries London Saver et al X England v I Primary ExammerCharles E. Van Horn Flled: Oct 1 1972 Assistant Examiner-David A. Simmons {21] AppL Nu: 300,351 Attorney, Agent, or Frrm-Neuman, wllllarns,

Anderson & Olson [30] Foreign Application Priority Data [57] ABSTRACT 3 fi i :i g The invention relates to the reinforcement of the ay mm mg 0m I edges of cementitious board and especially plasterboard. Reinforcing strips are secured to at least one 2 5 i ggg gifig edge of the lower sheet employed in the manufacture 156/39 6 156/78 of plasterboard and is incorporated with the sheet in 1 o i 2 the formed board as an edge reinforcement. The reinforcing strip may have any desired cross-section or profile but preferably has a channel section whereby [56] Reta-em cued the corners of the board are protected. lt may also be UNITED STATES PATENTS grooved longitudinally to provide a kerfed edge to the 1,731.116 10/1929 Utzman 156/39 X board which is useful when securing the boards by 772,483 8/]930 GflSWO|d.... 156/44 X means of concealed upports l,787,l63 l2/l930 New 4 r r l6l/44 3,357,146 l2/l967 Gartrell 52/309 7 Chums, 7 Drawing Figures PATENTED 3 SHEET PATENTED JUN 3 I975 SHEET PRODUCTION OF BUILDING BOARD The present invention relates to the production of building board, and more especially of board of cementitious material. such as plaster, having a reinforced edge.

For a variety of purposes it is desirable to make use of boards of cementitious material having reinforced edges. For example, in the construction of ceilings with concealed supports and inconspicuous joints between adjacent panels, it is desirable to use boards or panels having kerfs or channels along at least two opposite edges. The presence of such kerfs, however, weakens the edges of the board and it is therefore desirable that some form of reinforcement should be introduced, preferably at the time of manufacture.

In one conventional method for the manufacture of lined cementitious boards, for example plasterboard. a first lining sheet, commonly of paper, is supplied continuously to and advanced along a board-forming bed, the lateral edges of the sheet are folded upwards as the sheet advances, an aqueous slurry of gypsum plaster is deposited on the upper surface of the first sheet, a second lining sheet is laid over the first sheet and slurry, and the slurry is formed to the desired thickness by a pressure roller or other surface extending over the bed, the two facing sheets being secured together at their edges by adhesive.

In the manufacture of cementitious board in accordance with the present invention, a reinforcing strip is secured to at least one lateral edge of the first lining sheet, passes through the board-forming operation with the first sheet and is incorporated therewith as an edge reinforcement in the formed board.

In preferred embodiments of the invention, the reinforcing strip is supplied at the same rate as the first sheet and is secured to the upper surface of the edge of the sheet. As the sheet advances and its edges are folded upwards the strip is gradually rotated into the position it will occupy in the finished board.

Preferably, the reinforcing strip is pressed into contact with the first facing sheet by a pair of cooperating rollers having suitably profiled edges. An adhesive of rapid action for example a hot melt adhesive, is desirable.

The reinforcing strip may have any desired crosssection or profile, although it should not extend beyond the width of the board in which it is to be incorporated. As indicated above, a profile of particular instance is one adapted to reinforce an edge kerf in the board, and for this purpose the strip may be of kerf or channel section, preferably having lateral flanges at the edges of the kerf or channel to lie along the projecting edges of the core on either side of the kerf.

Such a channel section strip is preferably secured to the first sheet with the channel opening downwards on the upper surface of the edge region of the sheet. The channel section may be pressed into contact with the sheet by a pair of profiled edge rollers, the upper of which is grooved to receive the channel and the other of which has a peripheral bead corresponding in position to the opening of the channel. As the sheet ad vances and its edges are folded upwards the channel section is gradually rotated through a right angle until the opening is directed horizontally away from the board axis.

For the purpose of reinforcing the outer corners of the board edge it is desirable that the reinforcing strip should have flanges to form reinforced shoulders on the corners. Such flanges assist in the adhesion of the strip to the facing sheet and the strip may be treated to increase the degree of adhesion, for example by perforating it to enable small amounts of the adhesive in a liquid condition to pass through. Beads of adhesive formed in this way can also serve at a later stage in the process to provide a key for the cementitious material and so enhance the bond between the reinforcing strip and the core of the board. Further, the strip can have a profile which enhances its mechanical key to the core.

The invention will be described in greater detail, by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a diagrammatic side elevation of one example of apparatus for forming kerfed edge board by the method of this invention;

FIG. 2 is an enlarged side view and FIG. 3 an enlarged crosssection of the entry end of the boardforming bed;

FIGS. 4, 5 and 6 are enlarged sections of edges of finished boards having reinforcing strips of various sections', and

FIG. 7 is a section of a reinforcing strip having a keyenhancing profile.

In the apparatus shown in FIG. I, a flat conveyor or board-forming table 11 is supplied with a bottom sheet of paper 12 from a supply roll (not shown), the paper passing over an arcuate guide 13 to reach the table. Over the table are mounted a mixer 14 for a cementitious material and water, provided with discharge nozzles for the resulting slurry, and a squeeze roller 15 for gauging the thickness of the board formed, as in a conventional plasterboard machine. At the sides of the table, before the mixer 14 is reached, are folder plates I6 of conventional form to fold the edges of the bottom paper 12 and erect them to form a trough into which the slurry is deposited from the mixer.

Over the arcuate guide 13 are mounted scoring rollers 17 for scoring respective edges of the bottom paper 12 preparatory to folding, the scoring rollers being displaced from their conventional position at the beginning of the table. Also over the guide 13 are hot melt adhesive applicators 18 for each edge of the bottom paper.

Flanged channel-section kerf strips 20 are supplied continuously to the edges of the bottom paper 12, being advanced along the line of the table II and meeting the molten adhesive-coated edges of the paper with the channel-openings downwards. Immediately after contacting the paper, both paper and kerf strips pass between a pair of pressure rollers or discs 21 and 22 (better seen in FIG. 2 and still more clearly in FIG. 3) which press the kerf strips onto the paper for better adhesion thereto. The upper roller 21 has a peripheral groove 23 to accommodate the channel portion of the kerf strip and the lower roller 22 a peripheral bead 24 in a corresponding position but of reduced height. The paper 12 is pressed partly into the channel opening by the bead 24.

The kerf strips are preferably flanged, as shown in the drawings, and may conveniently be formed continu ously by forming roller and drawing dies located upstream of the board-forming table II (and not shown in the drawing). They are preferably formed of metal strip, for example of steel, which can in turn be supplied from a roll of long continuous lengths. After formation of the kerf strip it may be passed through a punch or other perforator disposed between the kerf forming mill and the board-forming table 11, whereby the flanges of the strip are perforated to assist adhesion to the paper and subsequently, also to the core of the board.

Another example of suitable metal for the kerf strips is aluminium or its alloys. Kerf strips of plastics material unaffected by the board-making process may also be used, although in this case they may be separately formed by methods depending upon the particular type of plastics to be used.

After leaving the rollers 21 and 22 the bottom paper 12 with its attach kerf strips passes along the table to the folder plates 16 and during this passage the kerf strips with the attached paper edges begin to rotate inwardly until, when the paper edges are brought to the upright position by the folders the channel openings of the kerf strips (although now covered by the paper) are directed horizontally outwardly. The slurry, for example of gypsum plaster, is then deposited by the mixer 14 on the upper surface of the paper 12 and the further folding of the paper edges, the application of a top paper 25 and the squeezing of the slurry within the paper to form board of the desired thickness then fol low substantially as in conventional plasterboard manu' facture.

After the board has been formed and has acquired a preliminary set, it is cut into lengths, as in the case of plasterboard. In the case of this invention, however, special means must be employed to cut the reinforced, kerfed edges. For example, cutting wheels mounted on a reciprocating head may be employed to cut the kerf strips, the head advancing with the formed board during the cutting operation and returning as the next length of board passes by. The remainder of the board can then be cut by more conventional cutters, which may be guided by automatic means to pass through gaps formed in the kerf strips by the special cutting wheels mentioned above. A horizontal edge slitter may also be provided to cut the paper overlying the channel openings of the kerf strips.

As shown in FIG. 3, the kerfed strip employed may have one flange offset behind the plane of the other. This enables the kerfed board to be mounted on flanged T or I supports with the visible edges of the board in close abutment, their recessed flanges leaving a narrow space to accommodate the web of the support. Since it is customary for the face paper of plasterboard to be provided by the bottom sheet in manufacture, the offset or recessed flange is preferably the outer flange of each kerf strip so that, after the paper has been folded it will be located at the rear surface of the formed board.

The edge of the board formed in accordance with the preferred procedure of this invention is shown in section in FIG. 4. The flanged kerf strip 20 in this case has perforations which have been punched from the outer face so as to produce a burr at the inner face of the flange. This, together with the bead 31 of adhesive formed when the strip 20 is initially pressed into contact with the bottom paper 12 carrying a layer of hot melt adhesive 32. enhances the bond of the kerf strip to the paper edge and subsequently affords a key whereby an enhanced bond is achieved between the kerf strip itself and the set core 33 of the cementitious board.

The method described for forming board with a kerfed channel can equally be used to form boards with reinforcing strips of different non-planar sections. Suitable modifications can be made to the shape of the pressure rollers 21 and 22 to ensure good adhesion of the strip to the bottom paper.

In FIG. 5 is shown a square-edged board. The profiled strip is a square channel 40 whose width is substantially the same as the thickness of the board. The square channel 40 is secured to the paper 12 by an adhesive 32.

FIG. 6 shows a board having a reinforcing strip 42 of right-angled profile secured to the paper 12 by an adhesive 32.

The reinforcing strip 44 shown in section in FIG. 7 is formed with a bulbous termination 45 of the channel 46. The bulb enhances the key of the strip to the core of a board in which it is incorporated.

What I claim is:

l. A method for the production of lined cementitious board comprising the steps of:

continuously advancing a first sheet in a generally horizontal plane; providing a reinforcing strip of rigid material formed with a section of desired non-planar profile;

supplying such reinforcing strip to the upper surface of at least one lateral edge of said first sheet and securing said strip to said edge with such profile in a first orientation relative to said plane;

depositing an aqueous slurry of cementitious material on the upper surface of said first sheet;

folding the lateral edges of said first sheet upwards as the sheet advances and rotating said strip therewith from said first orientation into the orientation and disposition said strip will have in the finished board, without alteration of the profile of said strip; laying a second sheet over said slurry and the upwardly folded lateral edges of said first sheet; forming said slurry to the desired thickness; and securing said two sheets together at their lateral edges whereby said strip is incorporated in the formed board.

2. A method according to claim 1 wherein the strip is secured to the sheet by a hot melt adhesive.

3. A method according to claim 1 wherein the strip is pressed into contact with the first facing sheet by a pair of cooperating rollers.

4. A method according to claim 1 wherein the width of the reinforcing strip is substantially equal to the thickness of the core of the board.

5. A method according to claim I wherein the reinforcing strip has a flanged channel section and is secured with the channel opening downwards on the upper surface of the first sheet in said first orientation.

6. A method according to claim I wherein the reinforcing strip is perforated.

7. A method according to claim I wherein the cementitious material is gypsum plaster. 

1. A method for the production of lined cementitious board comprising the steps of: continuously advancing a first sheet in a generally horizontal plane; providing a reinforcing strip of rigid material formed with a section of desired non-planar profile; supplying such reinforcing strip to the upper surface of at least one lateral edge of said first sheet and securing said strip to said edge with such profile in a first orientation relative to said plane; depositing an aqueous slurry of cementitious material on the upper surface of said first sheet; folding the lateral edges of said first sheet upwards as the sheet advances and rotating said strip therewith from said first orientation into the orientation and disposition said strip will have in the finished board, without alteration of the profile of said strip; laying a second sheet over said slurry and the upwardly folded lateral edges of said first sheet; forming said slurry to the desired thickness; and securing said two sheets together at their lateral edges whereby said strip is incorporated in the formed board.
 1. A METHOD FOR THE PRODUCTION OF LINED CEMENTITIOUS BOARD COMPRISING THE STEPS OF: CONTINUOUSLY ADVANCING A FIRST SHEET IN A GENERALLY HORIZONTAL PLANE; PROVIDING A REINFORCING STRIP OF RIGID MATERIAL FORMED WITH A SECTION OF DESIRED NON-PLANAR PROFILE; SUPPLYING SUCH REINFORCING STRIP TO THE UPPER SURFACE OF AT LEAST ONE LATERAL EDGE OF SAID FIRST SHEET AND SECURING SAID STRIP TO SAID EDGE WITH SUCH PROFILE IN A FIRST ORIENTATION RELATIVE TO SAID PLANE; DEPOSITING AN AQUEOUS SLURRY OF CEMENTITIOUS MATEIRAL ON THE UPPER SURFACE OF SAID FIRST SHEET;
 2. A method according to claim 1 wherein the strip is secured to the sheet by a hot melt adhesive.
 3. A method according to claim 1 wherein the strip is pressed into contact with the first facing sheet by a pair of cooperating rollers.
 4. A method according to claim 1 wherein the width of the reinforcing strip is substantially equal to the thickness of the core of the board.
 5. A method according to claim 1 wherein the reinforcing strip has a flanged channel section and is secured with the channel opening downwards on the upper surface of the first sheet in said first orientation.
 6. A method according to claim 1 wherein the reinforcing strip is perforated. 